Yoshiki Saito

Shimane University · Estuary Research Center

The presently active Yellow River (Huanghe) delta lobe has been forming since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaeria...

Taiwan’s setting of high mountains, steep gradients, frequent earthquakes, erodible lithology, and heavy rainfall represents an ideal site to focus on sedimentary processes of the deltas of small mountainous rivers (SMRs). Several SMRs in southwestern Taiwan have deposited a thick sedimentary succession in the composite Southwest Taiwan Delta (SWTD...

We reconstructed the centennial climate changes for the period of 9–7 cal ka BP in the upper region of the Changjiang (Yangtze) River Delta plain. A general warming and wetting trend from 8560 to 7220 cal yr BP was indicated by the decrease in Quercus (deciduous) and increases in Quercus (evergreen), Pinus , and Polypodiaceae spores. However, there...

This editorial introduces the “Holocene palaeoclimate” special collection, which examines the intricate relationship between human activities and climate systems throughout the Holocene. The collection highlights the significance of palaeoclimatic reconstructions, providing insights into past climate variability and extremes. By integrating multidi...

From the Abstract: The technosphere sensu Peter Haff [12] has auton- omous qualities, being not so much human-directed as incorporating dependent, strongly divided human soci- eties, while parasitizing its parent biosphere for energy and materials. By far the most recent and rapidly evolving of Earth’s ‘spheres’, it is also the most unsta- ble, rec...

Gravelly cyclic steps formed by turbidity currents have recently been widely recognised in the geological record. However, the comparison between modern and ancient gravelly cyclic steps remains challenging. In this study, the facies variations of gravelly cyclic steps deposited from turbidity currents in an outcrop of Miocene fan delta front depos...

River deltas ofer numerous ecosystem services and host an estimated global population of 350 million to more than 500 million inhabitants in over 100 countries. To maintain their sustainability into the future, deltas need to withstand sea-level rise from global warming, but human pressures and diminishing sediment supplies are exacerbating their v...

One of the remaining issues regarding the Anthropocene is the lack of stratigraphic evidence indicating when the cumulative human pressure from the early Holocene began to fundamentally change the Earth system. Herein, we compile anthropogenic fingerprints from various high-precision-dated proxy records for 137 global sites to determine the age of...

We synthesize research from complementary scientific fields to address the likely future extent and duration of the proposed Anthropocene epoch. Intensification of human-forced climate change began from about 1970 onwards with steepening increases in greenhouse gases, ocean acidification, global temperature and sea level, along with ice loss. The r...

Applying the basic principles of carbon chemistry and physics, along with a comprehensive understanding of past climate change, Steffen and colleagues confirmed in the Proceedings of the National Academy of Sciences 115, in 2018, that fossil fuel usage and resulting carbon emissions will cause substantial global warming into future millennia. The c...

A common sense: The Anthropocene was originally understood by Crutzen as not only representing humanity’s influence on Earth’s geological record (he was well aware of earlier anthropogenic impacts), but also reflecting a system with physical characteristics that had, since widespread industrialization, departed from the prolonged, relatively stable...

The "Great Acceleration" beginning in the mid-20th century provides the causal mechanism of the Anthro-pocene, which has been proposed as a new epoch of geological time beginning in 1952 CE. Here we identify key parameters and their diagnostic palaeontological signals of the Anthropocene, including the rapid breakdown of discrete biogeographical ra...

Abstract: The “Great Acceleration” of the mid-20th century provides the causal mechanism of the Anthropocene, which has been proposed as a new epoch of geological time beginning in 1952 CE. Here we identify key parameters and their diagnostic palaeontological signals of the Anthropocene, including the rapid breakdown of discrete biogeographical ran...

The Anthropocene Working Group (AWG) has concluded that the Anthropocene represents geological reality and should be linked with the plethora of stratigraphic proxies that initiate or show marked perturbations at around the 1950s, and should be defined using a Global boundary Stratotype Section and Point (GSSP). We propose formalizing the Anthropoc...

This part of the Anthropocene Working Group (AWG) submission proposes that the base of the Anthropocene should be defined as series/epoch, terminating the Holocene Series/Epoch with a single Crawfordian stage/age using a Global boundary Stratotype Section and Point (GSSP) in an annually varved Crawford Lake core, Ontario, Canada, defined at 17.5 cm...

Abstract: We synthesize research from complementary scientific fields to address the likely extent and duration of the proposed Anthropocene epoch. Ongoing intensification of human-forced climate change began in the mid-20th century, with steepening increases in greenhouse gases, ocean acidification, global temperature and sea level, along with the...

This is the Executive Summary of a report produced by the membership of the Anthropocene Working Group as part of a submission to the Subcommission on Quaternary Stratigraphy to seek formalisation of the Anthropocene as an epoch of geological time. It summarises the content of two reports and their associated appendices which provide a background t...

The Anthropocene as a prospective new, ongoing series/epoch must be defensible against all relevant concerns. We address the seven, still-relevant challenges posed to the Anthropocene Working Group by the Chair, International Commission on Stratigraphy (ICS), in 2014. (1) Concept or reality? The Anthropocene possesses a substantial, sharply distinc...

DNA metabarcoding (DNA-MB) targeting the whole plankton community is a promising approach in studies of sediment samples from water bodies, but its effectiveness in ancient material is not well demonstrated. We applied DNA-MB of plankton in a sediment core to reconstruct the paleo-environment of Lake Shinji, Japan, through a marine lagoon/freshwate...

To understand the Holocene sedimentary evolution of the Pearl River associated delta-estuary-shelf system, high-resolution seismic data were acquired from Lingdingyang Bay to the inner shelf. A Pearl-derived Holocene subaqueous clinoform developed over the pre-Holocene incised channel/valley network. Overlying the Holocene ravinement surface, progr...

Swindles et al. (2023) correctly point out that there are many conceptions of the ‘Anthropocene’ in use, and they argue that this flexibility in terminology is desirable. We agree that the multiple uses of this term have stimulated much scholarly debate, but we contend that precision in terminology is far more desirable than vagueness, and promotes...

Amino accelerators and antioxidants (AAL/Os) have become a suite of contaminants of emerging concern recently due to the accumulating evidence for their environmental occurrence and associated toxic potential. Nevertheless, data on sedimentary deposition of AAL/Os has remained scarce, particularly for regions beyond the North America. In the presen...

For assessment of the potential of the Beppu Bay sediments as a Global Boundaries Stratotype Section and Point (GSSP) candidate for the Anthropocene, we have integrated datasets of 99 proxies. The datasets for the sequences date back 100 years for most proxy records and 1300 years for several records. The cumulative number of occurrences of the ant...

High resolution pollen records in the northern edge of subtropical China are crucial to understand the pattern of postglacial vegetation change and climate transition. Here we present vegetation succession and climate change during 9.2–8.0 cal kyr BP based on sub-decennial scale pollen data. Pollen spectra show that Quercus (evergreen) & Cyclobalan...

Holocene climate change and human activities can lead to sediment composition variations. In this study, two drilled cores (VN and GA) from the Red River Delta, Vietnam, were subjected to magnetic measurement, as well as particle size, diffuse reflectance spectroscopy (DRS), and geochemical analyses, to infer Holocene sediment provenance changes. B...

Deltas are subaerial landforms that cap underlying deposits with subaqueous extensions that result from a river feeding sediment directly into a standing body of water at a rate that overwhelms any effective dispersal processes derived from the ambient basin. This definition encapsulates both the terrestrial surface expression and the geological fo...

The integration of the Sanmen Gorge marks the birth of the modern Yellow River, but the timing varies from the late Miocene-early Pliocene to the late Pleistocene (∼0.15 Ma) and the underlying forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change. Here, we report sedimentology, geochronology, and provenance data fr...

Due to accelerated river-derived sediment deficits, global deltas are presently under an increasing risk of being submerged. To address the fundamental need to save Earth's deltas, boosting riverine sediment supply can be considered a reasonable option, but only if the new supply of sediment is prolonged and greater than the opposing forces: sea le...

The Central Yellow Sea Mud (CYSM) archived important signals of changing regional environment and climate during the Holocene. We performed high-resolution analysis of two sediment cores taken from the CYSM including measurements of radiocarbon chronology and grain size, as well as the mineralogical and geochemical measurements on the sediment samp...

This chapter focuses on major deltas built by large rivers with high sediment discharge and discusses their morphology, sedimentology, and evolution based mainly on data from recent studies. A ternary diagram originally proposed by Galloway is the best‐known system for classifying deltas. It builds on a concept by Fisher, who subdivided deltas into...

Sediments of river deltas provide valuable records of past coastal environments. Optically-stimulated luminescence (OSL) dating has become an alternative to radiocarbon dating for constraining the sediment chronology in large deltas that allow for sufficient sunlight bleaching of sediments during the fluvial transport. However, its applicability to...

The global sediment cycle is a fundamental feature of the Earth system, balancing competing factors such as orogeny, physical–chemical erosion and human action. In this Review, values of the magnitudes of several sources and sinks within the cycle are suggested, although the record remains fragmented with uncertainties. Between 1950 and 2010, human...

The Pleistocene Series/Epoch of the Quaternary System/Period has been divided unofficially into three subseries/subepochs since at least the 1870s. On 30th January, 2020, the Executive Committee of the International Union of Geological Sciences ratified two proposals approved by the International Commission on Stratigraphy formalizing: 1) the Lower...

Limited information is known about organophosphate esters (OPEs) in sediments of the Dong Nai River System (DNRS) in Vietnam and the influences of complex hydro-sedimentary dynamics on their fate. In this study, 48 surface sediment samples were collected from the Dong Nai-Soai Rap River and its tributary Vam Co River for the determination of 11 tar...

Muddy coasts downdrift of large river mouths trap fine-grained sediments supplied from these rivers and have provided important settlement sites for prehistoric people, although the evolutionary history of such environments has not been well described. In this study, we integrate multi-proxy analyses (lithology, particle size, sedimentary structure...

To better understand the sedimentary facies of tide‐dominated deltas, a core dataset from the Ba Lai palaeochannel in the Mekong River Delta was obtained and studied. Nine sedimentary facies were identified and interpreted as representing the Late Holocene evolution of the Ba Lai palaeochannel, including its pre‐abandonment and post‐abandonment pha...

A high-resolution dinoflagellate cyst analysis on a sediment core GLW1D from the northern South China Sea (SCS) was performed to reconstruct paleoceanographic conditions over the last 12,500 years through qualitative, semi-quantitative, and quantitative methods. A modern dataset with 398 reference sites in the northern Pacific was assembled and use...

The Ba Lai distributary channel of the Mekong River Delta was abandoned and infilled with sediment during the Late Holocene, providing a unique opportunity to investigate the sediment fill, timing and mechanisms of channel abandonment in tide-dominated deltaic systems. Based on analysis and age dating of four sediment cores, we show that the channe...

The modern Huanghe Delta used to be the most rapid land-building delta in the world. Its evolution has become a global concern because the sediment load of the Huanghe has decreased sharply in recent decades. However, few studies have revealed the full picture of Huanghe Delta evolution because of a lack of systematic bathymetric data off the delta...

Tsunamis are generally considered to disturb the seafloor, rework surface sediments, and change seafloor environments. However, the response of the seafloor to such extreme wave events has not been fully elucidated. Herein, we compare the surface sediments before and after the 2011 Tohoku-oki tsunami on the Sendai shelf and demonstrate that both sa...

The Yellow River (Huanghe) is a major sediment source of sediment to the Bohai Sea and Yellow Sea, resulting in the formation of a large and dynamic delta complex. However, the river sediment discharge reaching the delta has decreased dramatically since the middle 1960s. This study examines the sediment accumulation and morphological changes of the...

Recent 200+ km progradation of the Mekong River delta over the last 6000 years has provided a sequence of incised-valley fills with insights into the sedimentary response of a large river system to sea-level changes since the Last Glacial Maximum (LGM). This study provides an analysis of comprehensive synthesis of the incised-valley and successive...

Today's deltas are impacted negatively by (1) accelerated subsidence (e.g., from ground fluid extraction), (2) global eustatic sea level rise, and (3) decreased sediment supply, which increasingly starves these landforms of sediment necessary to sustain their footprint. This growing vulnerability threatens many megacities that have developed due to...

Wet summers and dry winters are an essential feature of monsoon climates, but quantification of change in wet-dry seasonality through time is very challenging because most geological materials fail to record sub-annual environmental signals, instead integrating years, decades, or centuries. Here we quantify Asian wet-dry seasonality since the middl...

The Holocene evolution of the Krishna Delta was inferred using landform characteristics and 11 sediment cores with 59 Accelerator Mass Spectrometry ¹⁴C dates. The landform assemblages in a 5880 km² area of the Krishna Delta indicate an upper (landward) river-built fluvial plain and a lower (seaward) marine-built beach-ridge plain. Holocene sediment...

The Holocene sea-level history of the east coast of India is relatively unexplored. We analysed a 17.37-m-long sediment core from Kolleru Lake, a fresh waterbody located in a deltaic setting along the east coast of India, to reconstruct the climate, environmental, and sea-level history of the region. Sedimentary facies and pollen assemblages, with...

Studies on the sediment distribution along the fluvial to marine transition zone are rare and have focused on large-scale systems. Here, we report a case study from the Dong Nai River System (DNRS), a small-scale, tide-dominated river delta from southern Vietnam. The study is based on 80 channel bed sediment samples, together with channel depth, te...

Having developed in the later Quaternary Period, the Mui Ne dunefield, representing the upper-most portion of a major coastal barrier complex in SE Vietnam, formed by wind regimes associated with the Asian monsoon climate. The barrier complex is 100 km long and higher than 150 m in elevation but despite its large dimensions, research on its geomorp...

Estuarine fronts are the boundaries between different water masses at river mouths and play important roles in trapping suspended particles. Investigating the response of estuarine fronts to climate and sea-level changes during the Holocene could elucidate the evolution of complex hydro- and sediment-dynamic processes at river mouths. To assess the...

Based on high-resolution analysis to a 280-cm long sediment core obtained from the muddy area in the central Yellow Sea, we examined the provenance of muddy sediments and discussed the changing marine sedimentary environment since the middle Holocene. The results indicated that fine-grained sediments in the muddy area were mainly derived from the H...

Since the 1990s the Mekong River delta has suffered a large decline in sediment supply causing coastal erosion, following catchment disturbance through hydropower dam construction and sand extraction. However, our new geological reconstruction of 2500-years of delta shoreline changes show that serious coastal erosion actually started much earlier....

The Holocene sea-level history of the east coast of India is relatively unexplored. We analysed a 17.37-m-long sediment core from Kolleru Lake, a fresh waterbody located in a deltaic setting along the east coast of India, to reconstruct the climate, environmental, and sea-level history of the region. Sedimentary facies and pollen assemblages, with...

Intensive studies have been conducted globally in the past decades to understand the evolution of several large deltas. However, despite being one of the largest tropical deltas, the Irrawaddy (Ayeyarwady) Delta has received relatively little attention from the research community. To reduce this knowledge gap, this study aims to provide a comprehen...

Understanding the flux of riverine sediment is crucial not only to document the global terrestrial material budget but also to understand erosion patterns within the drainage basin under the impact of natural and anthropogenic forces. Here we reconstructed changes of sediment discharge in the Yellow River over the last 7000 years based on a large n...

The Red River Delta (RRD), one of the two largest deltas in Vietnam, has been severely affected by natural hazards induced by global climate change. Understanding the Holocene paleoshoreline is crucial in developing adaptive planning in response to future shoreline changes based on past natural shoreline changes. This study presents new data pertai...

This paper presents geochemical and grain-size records since the early Holocene in core ECS0702 with a fine chronology frame obtained from the Yangtze River subaqueous delta front. Since ~9500 cal yr BP, the proxy records of chemical weathering from the Yangtze River basin generally exhibit a Holocene optimum in the early Holocene, a weak East Asia...

Understanding the relationship between depositional processes and their products in the fluvial–marine transition zone in tide-dominated depositional systems is fundamental to improving environmental and stratigraphic interpretations of long-term sedimentary records. The distributary channels of the Mekong Delta represent a typical example of a com...

Along the fluvial to marine transition zone (FMTZ) of river deltas, the river-tidal dynamics exert a primary control on channel width, sinuosity, and bed elevation; however, other local factors, such as valley confinements, bifurcations, and confluences, can modify the channel morphology. Here, we report a case study of the major channel of the Ðồn...

Tidal changes in Tokyo Bay during the last 10,000 years were investigated by combining a numerical model with newly compiled model bathymetries for the present day, the early 20th century, and every 1000 years from 4000 to 10,000 years ago. Over this time period, sea level has changed by more than 30 m, and the coastline has shifted 50–60 km. Tides...

Along their fluvial to marine transition zone, tide-dominated river deltas show upstream to downstream trends in channel width, sinuosity, and depth, which at present have been only partially reported. This review article aims to describe these morphological trends from five modern tide-dominated river deltas using original data collected from sate...

The B2 (B2G) and I4 sediment cores recovered from the centre of the distal mud area of the East China Sea (ECS) were analysed for grain size distribution. Proxies for environmentally sensitive grain size components (ESGSC) retrieved from the composite B2 core, namely, variations in the volumetric content and mean grain size of specific grain size f...

The Yangtze (Changjiang) mega-delta, China, has a high risk of coastal erosion owing to the recent high rate of relative sea-level rise and reduced sediment supply. The study of the Holocene evolution of the delta can provide information about its response to rapid sea-level rise and changes in sediment supply caused by climate or human activity, a...

A dataset of 176 channel bed sediment samples allowed a detailed analysis of mud pebbles (defined as mud clasts ranging in size from 2 to 64 mm) forming along the fluvial to marine transition zone (FMTZ) of the Mekong River delta. These mud pebbles are typically up to 4 cm in size, spheroidal to subspherical in shape, well rounded, and well sorted;...

The area of coastal rivers with a combination of fluvial, tidal and wave processes is defined as the fluvial to marine transition zone and can extend up to several hundreds of kilometres. The aim of this study is to improve the understanding of sediment distribution and depositional processes along the fluvial to marine transition zone using a comp...

The South Yellow Sea (SYS) Basin, which is part of the West Pacific Continental Margin, began to form in the late Mesozoic to early Cenozoic as a result of regional tectonic activity in Asia. The pre-Middle Pleistocene sedimentary history of the area remains poorly understood or controversial, mainly due to a lack of long borehole cores penetrating...

Understanding past relative sea-level (RSL) changes is crucial for predicting future coastal evolution, particularly within the context of accelerated melting of polar ice sheets due to global warming. RSL records are scarce in many regions along the Pacific coast. Here, we present a Holocene RSL curve for the west coast of South Korea based on det...

The mid- to late-Holocene monsoon decline led to aridification of the Indian Peninsula impacting the early agricultural practices in the region. Our analysis of organic carbon, mineral magnetic properties and AMS ¹⁴C dating of a 54.2-m-long sediment core (CY) from the Godavari Delta, India, showed changes in the organic carbon source and sediment p...

As the world’s third largest delta and one of the world's most important biodiversity hotspots, the Mekong Delta provides both ecological and food security for its inhabitants. Nevertheless, the delta has been threatened by climate change and human activities, particularly the proliferation of hydropower development across the Mekong Basin since th...